EXPERIMENT - 1
AIM: TO FIND OUT CRITICAL SPEED EXPERIMENTALLY AND TO COMPARE
THE WHIRLING SPEED OF A SHAFT.
EQUIPMENTS: TACHOMETER, SHAFT, END FIXING ARRANGEMENT ETC.
THEORY: THIS APPARATUS IS DEVELOPED FOR THE DEMONSTRATION OF A
WHIRLING PHENOMENON. THE SHAFT CAN BE TESTED FOR DIFFERENT END CONDITIONS. THE
APPARATUS CONSISTS OF A FRAME TO SUPPORT ITS DRIVING MOTOR, END FIXING AND
SLIDING BLOCKS ETC. A SPECIAL DESIGN IS PROVIDED TO CLEAR OUT THE TESTING OF
BEARING OF MOTOR SPINDLE FROM THESE TESTING SHAFTS. THE SPECIAL DESIGN FEATURES
OF THIS EQUIPMENT ARE AS FOLLOW:
A.
COUPLING
A FLEXIBLE SHAFT IS USED TO DRIVE THE TEST SHAFT FROM MOTOR.
B.
BALL BEARING FIXING ENDS.
THE END FIXES THE SHAFT WHILE IT ROTATES. THIS CAN BE REPLACED
WITHIN A SHORT TIME WITH THE HELP OF THIS UNIT. THE FIXING ENDS PROVIDE CHANGE
OF END FIXING CONDITION OF THE ROTATING SHAFT AS PER THE REQUIREMENT.
C.
SHAFT SUPPLIED WITH THE EQUIPMENT
POLISHED STEEL SHAFT IS SUPPLIED WITH THE MACHINE. THE DIMENSIONS
BEING AS UNDER:
SHAFT
NO.
|
DIAMETER
(APPROX)
|
LENGTH(APPROX)
|
1.
|
4.0 MM
|
900 MM
|
2.
|
4.7 MM
|
900 MM
|
END FIXING ARRANGEMENT
AT MOTOR END AS WELL AS
TAIL END DIFFERENT END CONDITIONS CAN BE DEVELOPED BY MAKING USE OF DIFFERENT
FIXING BLOCKS.
·
SUPPORTED END CONDITIONS -
MAKE USE OF END BLOCK WITH SINGLE SELF ALIGNING BEARINGS.
·
FIXED END CONDITION - MAKE
USE OF END BLOCK WITH DOUBLE BEARING.
GUARDS D1 AND D2:
THE GUARDS D1 AND D2 CAN BE
FIXED AT ANY POSITION ON THE SUPPORTING BAR FRAME WHICH FITS ON SIDE SUPPORTS
F. ROTATING SHAFTS ARE TO BE FITTED IN BLOCKS IN A AND B STANDS.
SPEED CONTROL OF DRIVING MOTOR:
THE DRIVING MOTOR IS 230V,
DC 1/6 HP, 3000 RPM, UNIVERSAL MOTOR AND SPEED CONTROL UNIT IS A DIMMER STATE
OF 240V, 2 AMPS, 50 C/S.
MEASUREMENT OF SPEED:
TO MEASURE THE SPEED OF THE
ROTATING SHAFT A SIMPLE TACHOMETER MAY BE USED ON THE OPPOSITE SIDE OF THE
SHAFT EXTENSION OF THE MOTOR.
WHIRLING OF ELASTIC SHAFT:
IF L = LENGTH
OF THE SHAFT IN CMS.
E = YOUNG’S
MODULE KG/CM2 2.060 X 106
|
I = 2ND MOMENT
OF INERTIA OF THE SHAFT CM4
W = WEIGHT OF THE
SHAFT PER UNIT LENGTH KG/CM.
G = ACCELERATION
DUE TO GRAVITY OF CMS/SEC2 = 981
THEN THE FREQUENCY OF
VIBRATION FOR THE VARIOUS MODES IS GIVEN BY THE EQUATION:
E.I.G
F = K X --------
W.L.4
END
CONDITION
|
VALUE OF K
|
||
1ST MODE
|
2ND MODE
|
||
FIXED , SUPPORTED
FIXED , FIXED
|
1.47
1.57
|
2.56
2.46
|
|
DATA:
SHAFT
DIA
|
I
= CM4
|
W
= KG/CM
|
3.8 MM
5.0 MM
|
X 10-4
X 10-4
|
0.15 X 10-2
0.28 X 10-2
|
CALCULATIONS:
a) BOTH ENDS OF SHAFTS FREE (SUPPORTED) 1ST AND 2ND MODE
OF VIBRATION CAN BE OBSERVED OF SHAFTS WITH 3/16” DIA AND ¼” DIA.
b) ONE END OF SHAFT FIXED AND THE OTHER FREE; 1ST AND
2ND MODE OF VIBRATION CAN BE OBSERVED ON SHAFT WITH 3/16” DIA.
c) BOTH ENDS OF SHAFT FIXED- 2ND MODE OF VIBRATION
CANNOT BE OBSERVED ON ANY OF THE SHAFTS AS THE SPEEDS ARE VERY HIGH AND HENCE BEYOND
THE RANGE OF THE APPARATUS.
FIXED – FIXED
·
DIAMETER OF BRASS ROD = 0.4
CM
·
WEIGHT = 150 GRM = KG/CM =
0.0015
·
YOUNG MODULUS E = 2.06 X 106
S.NO.
|
SPEED RPM
1ST MODE
|
VALUE OF K
|
I=(ΠD4)/64
|
WEIGHT IN GRAMS
|
FTH =
K.(EIG)/W
|
FACT =
RPM/TIME
|
1
|
||||||
2
|
·
DIAMETER OF BRASS ROD =
0.47 CM
·
WEIGHT = 190 GRAM = KG/CM =
0.0019
·
YOUNG MODULUS E = 2.06 X 106
S.NO.
|
SPEED RPM
2ND MODE
|
VALUE OF K
|
I=(ΠD4)/64
|
WEIGHT IN GRAMS
|
FTH =
K.(EIG)/W
|
|||
1
|
||||||||
2
|
||||||||
SUPPORTED – FIXED
·
DIAMETER OF BRASS ROD = 0.4
CM
·
WEIGHT = 190 GRAM = KG/CM =
0.0019
·
YOUNG MODULUS E = 2.06 X 106
S.
NO.
|
SPEED RPM
1ST MODE
|
SPEED RPM
2ND MODE
|
VALUE OF K
|
VALUE OF K
|
I=(ΠD4)/64
|
WEIGHT
IN GRAMS
|
FTH =
K.(EIG)/WL4
|
FTH =
K.(EIG)/WL4
|
FACT=
RPM/TIME
|
FACT=
RPM/TIME
|
1.
|
||||||||||
2.
|
·
DIAMETER OF BRASS ROD =
0.47 CM
·
WEIGHT = 140 GRAM = KG/CM =
0.0014
·
YOUNG MODULUS E = 2.06 X 106
S.NO.
|
SPEED RPM
1ST MODE
|
SPEED RPM
2ND MODE
|
VALUE OF K
|
VALUE OF K
|
I=(ΠD4)/64
|
WT.
IN GRAMS
|
FTH =
K.(EIG)/WL4
|
FTH =
K.(EIG)/WL4
|
FACT=
RPM/TIME
|
FACT=
RPM/TIME
|
||
1.
|
||||||||||||
2.
|
||||||||||||
EXPERIMENT - 2
AIM: TO FIND EXPERIMENTALLY THE GYROSCOPIC COUPLE ON MOTORIZED
GYROSCOPE AND COMPARE WITH APPLIED COUPLE.
APPARATUS USED: MOTORIZED GYROSCOPE,
TACHOMETER.
INTRODUCTION:
A.
AXIS OF SPAN
IF A BODY IS REVOLVING ABOUT AN AXIS, LATTER IS KNOWN AS AXIS OF
SPIN.
B.
PRECESSION
PRECESSION MEANS THE ROTATION ABOUT THE THIRD AXIS OZ WHICH IS
PERPENDICULAR TO BOTH THE AXIS OF SPIN OX AND THAT OF COUPLE OY.
C.
AXIS OF PRECESSION
THE THIRD AXIS OX IS PERPENDICULAR TO BOTH THE AXIS OF SPIN OX AND
THAT OF COUPLE OY IS KNOWN AS AXIS OF PRECESSION.
D.
GYROSCOPE
IT IS A BODY WHILE SPINNING ABOUT AN AXIS IS FREE TO ROTATE IN
OTHER DIRECTION UNDER THE ACTION OF EXTERNAL FORCE.
EXAMPLE: LOCOMOTIVE, AUTOMOBILE
AND AEROPLANE MAKING A TURN. IN CERTAIN CASES THE GYROSCOPIC FORCES ARE
UNDESIRABLE WHEREAS IN OTHER CASES THE GYROSCOPIC EFFECT MAY BE UTILIZED IN
DEVELOPING DESIRABLE.
E.
GYROSCOPIC EFFECT
TO A BODY REVOLVING ABOUT AN AXIS SAY OX (REFER FIG. 1) IF A
COUPLE REPRESENTED BY A VECTOR OY PERPENDICULAR TO OX IS APPLIED, THEN THE BODY
TIES TO PROCESS ABOUT AN AXIS OZ WHICH IS PERPENDICULAR BOTH TO OX AND OY. THUS
THE PLANE OF SPIN, PLANE OF PRECESSION AND PLANE OF GYROSCOPIC COUPLE ARE
MUTUALLY PERPENDICULAR.
THE ABOVE
COMBINED EFFECT IS KNOWN AS PROCESSIONAL OR GYROSCOPIC EFFECT.
GYROSCOPIC COUPLE OF A PLANE DISC:
LET A DISC OF WEIGHT ‘W’
HAVING MOMENT OF INERTIA I BE SPINNING AT AN ANGULAR VELOCITY ABOUT AXIS OX IN
ANTI-CLOCKWISE DIRECTION VIEWING FROM FRONT (REFER FIG.2). THEREFORE THE
ANGULAR MOMENTUM OF THE DISC IS I. APPLYING RIGHT HAND , SCREW RULE, THE SENSE
OR VECTOR REPRESENTING THE ANGULAR MOMENTUM OR THE DISC WHICH IS ALSO A VECTOR
QUANTITY WILL BE IN THE DIRECTION OX AS SHONE . A COUPLE WHOSE AXIS IS OY
PERPENDICULAR TO OX AND IS THE PLANE Z, IS NOW APPLIED TO PROCESS THE AXIS OX.
LET AXIS OX TURN THROUGH A
SMALL ANGULAR DISPLACEMENT FROM OX TO OX’ IN TIME Δ T. THE COUPLE APPLIED
PRODUCES A CHANGE IS DUE TO THE VELOCITY OF PRECESSION. THEREFORE OX REPRESENTS
THE ANGULAR MOMENTUM AFTER TIME Δ T.
CHANGE OF ANGULAR MOMENT =
OX’-OX =XX’
OR RATE OF CHANGE OF
ANGULAR MOMENTUM= ANGULAR DISPLACEMENT/TIME
= XX’/T = OX* ΔΘ/ΔT
AS XX’=OX *Δ Θ IN DIRECTION
OF XX’
NOW AS RATE OF CHANGE OF
ANGULAR MOMENTUM
=COUPLE APPLIED =C=T
WE GET
T = O × ΔΘ /ΔT
BUT OX = I.Ω
WHERE I = MOMENT OF INERTIA
OF DISC AND
Ω = ANGULAR VELOCITY OF DISC.
AND IN THE LIMIT WHEN IT IS VERY SMALL, WE HAVE
Θ/T = DΘ/DT
AND DΘ/DT = ΩP = ANGULAR
VELOCITY OF PRECESSION OF YOKE AT VERTICAL AXIS.
THUS WE GET T = I × Ω × WP
THE DIRECTION OF THE COUPLE
APPLIED ON THE BODY IS CLOCKWISE WHEN LOOKING IN THE DIRECTION XX AND IN THE
LIMIT IS PERPENDICULAR TO THE AXIS OF Ω AND ΩP. THE REACTION COUPLE EXERTED BY
THE BODY ON ITS FRAME IS EQUAL IN MAGNITUDE TO THAT OF C, BUT OPPOSITE IN
DIRECTION.
RULE NO. 1
“THE SPINNING BODY EXERTS A
TORQUE OR COUPLE IN SUCH A DIRECTION WHICH TENDS TO MAKE THE AXIS OF SPIN
COINCIDES WITH THAT OF THE PRECESSION”.
TO STUDY THE RULE OF
GYROSCOPE BEHAVIOR FOLLOWING PROCEDURE MAY BE ADOPTED:
i.
BALANCE THE INITIAL
HORIZONTAL POSITION OF THE ROTOR.
ii. START THE MOTOR BY
INCREASING THE VOLTAGE WITH THE AUTO-TRANSFORMER, AND WEIGHT UNTILL IT ATTAINS
CONSTANT SPEED.
iii.
PRESS THE YOKE FRAME NO.2
ABOUT VERTICAL AXIS BY AN APPLIED NECESSARY FORCE BY HAND TO THE SAME (IN THE
CLOCKWISE SENSE SEEN FROM ABOVE).
iv.
IT WILL BE OBSERVED THAT
THE ROTOR FRAME SWINGS ABOUT THE HORIZONTAL AXIS Y.Y MOTOR.
v.
SIDE IS SEEN COMING UPWARDS
AND THE WEIGHT PAN SIDE GOING DOWNWARDS.
vi.
ROTATE THE VERTICAL YOKE
AXIS IN THE ANTI-CLOCKWISE DIRECTION SEEN FROM ABOVE AND OBSERVE THAT THE ROTOR
FRAME SWING IN OPPOSITE SENSE (AS COMPARED TO THAT IN PREVIOUS CASE FOLLOWING
THE ABOVE RULE).
RULE NO. 2:
“ THE SPINNING BODY
PROCESSES IN SUCH A WAY AS TO MAKE THE AXIS OF SPIN COINCIDE WITH THAT OF SPIN
COINCIDE WITH THAT OF THE COUPLE APPLIED, THROUGH 90 TURN”
i.
BALANCE THE ROTOR POSITION
ON THE HORIZONTAL FRAME.
ii. START THE MOTOR BY
INCREASING THE VOLTAGE WITH THE AUTO-TRANSFORMER AND WAIT TILL THE DISC ATTAINS
CONSTANT SPEED.
iii. PUT WEIGHT (0.5 KG, 1KG OR
2KG) IN WEIGHT PAN, AND START STOP WATCHTO NOTE THE TIME IN SECOND REQUIRED FOR
PROCESSION, THROUGH 60 OR 45 ETC.
iv.
THE VERTICAL YOKE PROCESSES
ABOUT OZ AXIS AS PER THE RULE NO. 2.
v.
SPEED MAY BE MEASURED BY
THE TACHOMETER PROVIDED ON THE CONTROL PANEL.
vi.
ENTER THE OBSERVATION IN
THE TABLE.
MOTORIZED GYROSCOPE APPARATUS:
·
M WEIGHT OF
DISC 4.800 KG
·
D DIA OF THE
PLATE 28.5 CM
·
DISTANCE WEIGHT POINT TO
DISC CENTER 22.5 CM
·
TIME 60 SEC.
·
G 9.81 M/S
S.
NO.
|
RPM
|
Φ2
|
Φ1
|
Φ =
(Φ2-Φ1)
|
WT.
|
I=MXD2/8G
|
W=(2ΠN/60)
|
WP=ΠΦ/180T
|
TTH=IXWXWP
|
TACT=X
DISTANCE
|
1
|
||||||||||
2
|
||||||||||
3
|
EXPERIMENT - 3
AIM: TO PERFORM THE EXPERIMENT THE UNBALANCED COUPLE AND FORCE.
DESCRIPTION: THE APPARATUS BASICALLY CONSIST OF A STEEL SHAFT MOUNTED IN BALL
BEARING IN A STIFF RECTANGULAR MAIN FRAME. A SET OF SIX BLOCKS OF DIFF. WEIGHTS
IS PROVIDED AND MAY BE CLAMPED IN ANY POSITION ON THE SHAFT AND ALSO BE EASILY
DETACHED FROM THE SHAFT.
A DISC CARRYING A CIRCULAR
PROTECTOR SCALE IS FITTED ON ONE SIDE OF THE RACTANGULAR FRAME. SHAFT CARRIES A
DISC AND RIM OF THE DISC IS GROOVED TO TAKE A LIGHT CORD PROVIDED WITH TWO
CYLINDERICAL METAL CONTAINERS OF EXACTLY THE SAME WEIGHT.
A SCALE IS FITTED TO THE
LOWER MEMBER OF THE MAIN FRAME AND WHEN USED IN CONJUCTION WITH THE CIRCULAR
PROTACTOR SCALE, ALLOWS THE EXACT LONGITUDINAL AND ANGULAR POSITION OF EACH
ADJUSTABLE BLOCK TO BE DETERMINED.
THE SHAFT IS DRIVEN BY A
230 VOLTS SINGLE PHASE 50 CYCLES ELECTRIC MOTOR, MOUNTED UNDER THE MAIN FRAME,
THROUGH A BELT.
FOR STATIC BALANCING OF
INDIVIDUAL WEIGHTS THE MAIN FRAME IS SUSPENDED TO THE SUPPORT FRAME BY CHAINS
AND IN THIS POSITION THE MOTOR DRIVING BELT IS REMOVED.
FOR DYNAMIC BALANCING OF
THE ROTATING MASS SYSTEM THE MAIN FRAME IS SUSPENDED FROM THE SUPPORT FRAME BY
TWO SHORT LINKS SUCH THAT THE MAIN FRAME AND THE SUPPORTING FRAME ARE IN THE
SAME PLANE
PROCEDURE:
STATIC BALANCING
REMOVE THE DRIVE BELT. THE
VALUE OF WR. FOR EACH BLOCK IS DETERMINED BY CLAMPING EACH BLOCK IN TURN ON THE
SHAFT AND WITH THE CORD AND CONTAINER SYSTEM SUSPENDED OVER THE PROTACTOR DISC,
THE NUMBER OF STEEL BALLS, WHICH ARE OF EQUAL WEIGHT, ARE PLACED INTO ONE OF
THE CONTAINERS TO EXACTLY BALANCE THE BLOCK ON THE SHAFT. WHEN THE BLOCK
BECOMES HORIZONTAL, THE NUMBER OF BALLS ‘N’ WILL GIVE THE VALUE OF WR. FOR THE
BLOCK.
FOR FINDING OUT ‘WR’ DURING
STATIC BALANCING PROCEED AS FOLLOWS:
i.
REMOVE THE BELT.
ii. SCREWED THE COMBINED HOOK
TO THE PULLEY WITH GROOVE (THIS PULLEY IS DIFFERENT THAN THE BELT PULLEY).
iii.
ATTACH THE CORD – ENDS OF
THE PANS TO THE ABOVE COMBINED HOOK.
iv.
ATTACH THE BLOCK NO. 1 TO
THE SHAFT AT ANY CONVENIENT POSITION AND IN VERTICAL DOWNWARD DIRECTION.
v.
PUT STEEL BALLS IN ONE OF
THE PANS TILL THE BLOCK STARTS MOVING UP (UPTO HORIZONTAL POSITION).
vi.
NUMBER OF BALLS GIVE THE
‘WR’ VALUE OF BLOCK 1. REPEAT THIS 2-3 TIMES AND FIND THE AVERAGE NO. OF BALLS.
vii.
REPEAT THE PROCEDURE FOR
OTHER BLOCKS
STATIC & BALANCING OF 4 BLOCKS
OBTAIN STATIC BALANCE OF A
SET OF FOUR BLOCKS WITH UNBALANCE AS SHOWN BY PROPERLY POSITIONING THEM IN
ANGULAR AND LATERAL POSITION ON THE SHAFT.
NO.
|
UNBALANCE
(WR. PRODUCT)
|
1.
|
124
|
2.
|
122
|
3.
|
120
|
4.
|
117
|
DISTANCE BETWEEN EACH BLOCK
IS 2 CM. THE ARRANGEMENT IS AS SHOWN IN FIG.
FORCE POLYGON
ANGULAR POSITION OF NO. 3
BLOCK IS OBTAINED FROM THE FORCE POLYGON AND ITS MAGNITUDE IS ALSO OBTAINED
F3 = 70.
ADJUST ALL ANGULAR AND LATERAL POSITION PROPERLY AND FIND THAT THE SHAFT
ROTATES WITHOUT VIBRATION.
FORCE POLYGON
S.NO.
|
WT.
NO.
|
WT.
|
DISTANCE
|
COUPLE
|
ANGLE
|
1
|
4
|
124
|
0
|
0
|
189
|
2
|
3
|
122
|
2
|
244
|
0
|
3
|
2
|
120
|
4
|
480
|
33
|
4
|
1
|
117
|
6
|
702
|
206
|
EXPERIMENT - 4
OBJECTIVE: TO FIND THE SPEED AND TORQUE OF DIFFERENT GEARS IN AN
EPICYCLIC GEAR TRAIN.
SPECIFICATONS:
i.
GEAR TRAIN : SUN
GEAR : 14 TEETH
ii.
PLANT GEAR: 21 TEETH (2
NOS.)
iii.
INTERNAL GEAR
WITH : 56 TEETH
TORQUE MEASUREMENT
·
INPUT TORQUE – MOTOR
CURRENT CALIBRATED FOR MOTOR TORQUE.
·
PLANT CARRIER - PULLEY
OF 50 MM DIA AND SPRING BALANCE.
·
INTERNAL GEAR
- PULLEY, 120 MM DIA AND SPRING BALANCES.
·
BOTH PULLEYS ARE PROVIDED
WITH ROPE OF 12
·
MM DIA
·
DRIVE MOTOR - 1HP DC
MOTOR RPM MOTOR OPERATING ON 220 VOLTS
·
50 HZ SUPLLY, DRIVING THE
SUN GEAR.
MOTOR CALIBERATION CHART
CRURENT(AMPS)
|
TORQUE
|
1.00
|
0.5
|
1.20
|
1.5
|
1.40
|
2.5
|
1.60
|
3.0
|
1.80
|
4.0
|
2.00
|
5.0
|
2.20
|
6.0
|
THEORY:
WHENEVER THE DISTANCE
BETWEEN THE DRIVING AND DRIVEN MEMBER,(BOTH SHAFTS ARE NOT OPERATING ON THE
SAME AXIS)IS SMALL OR WHEN A POSITIVE SLIP LESS DRIVE IS REQUIRED , GEAR DRIVES
ARE USED .SUCH A COMBINATION OF TWO OR MORE GEARS IS CALLED GEAR TRAIN .GEAR
TRAINS MAY BE SIMPLE , COMPOUND OR EPICYCLIC GEAR TRAINS .THE AXIS OF
GEARS HAVE FIXED POSITION RELATIVE TO EACH OTHER. BUT IN EPICYCLIC GEAR TRAINS,
THE AXIS OF GEARS MAY HAVE RELATIVE MOTION TO EACH OTHER.
THE APPARATUS CONSIST OF
SUN AND PLANET GEAR TYPE EPICYCLIC GEAR TRAIN .A DRIVING MOTOR DRIVES THE SUN
WHEEL. THE PLANATORY GEARS, WHICH MESH WITH THE SUN GEAR AND MOUNTED ON PINS,
WHICH ARE FITTED TO PLANET CARRIERS PULLEY .EXTERNALLY, PLANET GEAR MESH WITH
THE INTERNAL GEAR WHICH IS MOUNTED OVER A SHAFT .THIS SHAFT ALSO CARRIES A
PULLEY. BOTH PULLIES ARE PROVIDED WITH ROPE BRAKE WITH SPRING BALANCES, SO THAT
EITHER PLANET CARRIES PULLEY OR INTERNAL GEAR PULLEY CAN BE HELD STATIONARY AND
OUTPUT TORQUE WITH HOLDING TORQUE CAN BE MEASURED .INPUT TORQUE HAS BEEN
CALIBERATED IN TERMS OF MOTOR CURRENT.
PROCEDURE
i.
CHECK THE NUT BOLTS FOR
TIGHTENING (NORMALLY ALL NUT-BOLTS ARE TIGHTENED) CONNECT THE ELECTRICAL SUPPLY
TO THE UNIT AND START THE UNIT.
ii.
TIGHTEN THE ROPE ON PLANET
CARRIER PULLEY SO THAT IT DOSE NOT ROTATE. NOW, SLIGHTLY TIGHTEN THE ROPE OVER
INTERNAL GEAR PULLEY.
iii.
NOTE DOWN THE
OBSERVATIONS. REPEAT THE PROCEDURE FOR DIFFERENT TORQUES.
(NOTE: WHEN ROPE ON INTERNAL GEAR PULLEY IS TIGHTENED, PLANET
CARRIER STARTS ROTATING. KEEP THE TENSION OF THE ROPE OVER THE PULLEY
(INTERNAL GEAR PULLEY) SO THAT IT JUST DOSE NOT ROTATE)
iv.
NOW, HOLD THE CARRIER
PULLEY AND LET INTERNAL GEAR PULLEY TO ROTATE.
v.
REPEAT THE SAME PROCEDURE
FOR DIFFERENT TORQUES AND COMPLETE THE OBSERVATION TABLE.
CALCULATIONS:
LET US CALOCULATE THE SPEED
RATIO, USING TABULAR METHOD.
ASSUME PLANET CARRIER ‘C’
LOCKED AND SUN GEAR GIVEN ONE REVOLUTION.
S. NO.
|
OPERATION
|
PLANETCARRIER
C
|
SUN GEAR S
14
|
PLANET
GEAR
P 21
|
INTERNAL GEAR
I 156
|
01.
|
PLANET CARRIER LOCKED SUN GEAR GIVEN
1 ROTATION
|
0
|
+1
|
-TS
---------
TP
|
-TS TP -TS
--- --- = -----
TP
T1 T1
|
02.
|
MULTIPLY BY ‘X’
|
0
|
X
|
-TS
--------- X
TP
|
-TS
-------- X
T1
|
03.
|
ADD ‘Y’ TO ALL COLUMNS
|
0
|
Y + X
|
Y -(TS/TP)
X
|
Y - (TS/T1) X
|
I.
CONDITION 1 (PLANET CARRIER LOCKED)
IN THIS CONDITION, INTERNAL GEAR MAKES [-(TS T1) X]
REVOLUTIONS OF SUN GEAR.
HENCE,
ANGULAR VELOCITY RATIO.
NS WS X T1
---- = ---- = ---------- = ----
N1 W1 (-TS/T1)
X TS
-T1 56
= ----
= -------- = -4
TS 14
HENCE, INTERNAL GEAR MAKES ONE REVOLUTION FOR 4 REVOLUTIONS OF SUN
GEAR. THE NEGATIVE SIGN INDICATES THAT BOTH THE GEARS REVOLUTION IN REVERSE
DIRECTION.
II.
CONDITION-2 (INTERNAL GEAR LOCKED)
IN THIS
CONNECTION, LET US TAKE ONE REVOLUTION OF PLANET CARRIER.
Y=1 & Y -TS/T1 X=0
Y = TS/T1
PUTTING THE VALUE OF ‘Y’
TS/T1 X=1
X=T1/14 = 56/ =4
ALSO, PLANET CARRIER MAKES ‘Y’ REVOLUTIONS FOR (Y+X) REVOLUTIONS
OF SUN GEAR.
HENCE, ANGULAR VELOCITY RATIO.
NS/NC= WS/WC= Y+X/Y
WHERE ‘NS’ AND ‘NC’ ARE THE SPEEDS OF SUN AND PLANET CARRIER
RESPECTIVELY.
=4+1/1 =5
III.
TORQUE
LET, TS = INPUT TORQUE
TC = TORQUE ON PLANET CARRIER
T1 = TORQUE ON INTERNAL GEAR
IF FRICTION IS NEGLECTED.
INPUT POWER = OUTPUT POWER.
TSWS +TCWC + TIWI = 0
EITHER WC OR WI WILL BE ZERO
HENCE3, TS.WS = TC.WC (OR TI.WI)
IV.
WITH THE CALIBRATION CHART OF MOTOR, FIND OUT TORQUE AT THE
CURRENT READING.TS
·
TORQUE ON THE PLANET CARRIED
TC = [0.05+0.012/2]X
9.81XS.B.
DIFFERENCE
·
TORQUE ON INTERNAL GEAR
TI = [0.120+0.022/2]X9.81XS.B.
DIFFERENCE
TC = TS + TI
PRECAUTIONS:
·
DO NOT LOAD THE MOTOR ABOVE
1.9AMP. CURRENT.
·
BEFORE STARTING THE EXPERIMENT,
PUT SOME LUBRICATING OIL TO GEARS & BEARINGS.
·
OPERATE ALL THE SWITCHES
AND CONTROLS GENT.
EXPERIMENT - 5
AIM:-TO PERFORM EXPERIMENT ON WATT AND PORTER GOVERNORS TO PREPARE
PERFORMANCE CHARACTERISTIC CURVES, AND TO FIND STABILITY & SENSITIVITY.
APPARATUS USED: - WATT AND PORTER GOVERNORS.
INTRODUCTION & THEORY: - THE FUNCTION OF A GOVERNOR IS TO REGULATE THE MEAN SPEED OF AN
ENGINE, WHEN THERE ARE VARIATIONS IN THE LOAD E.G. WHEN THE LOAD ON AN ENGINE
INCREASES, ITS SPEED DECREASES, THEREFORE IT BECOMES NECESSARY TO INCREASE THE
SUPPLY OF WORKING FLUID. WHEN THE LOAD ON THE ENGINE DECREASES, ITS SPEED
INCREASES AND THUS LESS WORKING FLUID IS REQUIRED. THE GOVERNOR AUTOMATICALLY
CONTROLS THE SUPPLY OF WORKING FLUID TO THE ENGINE WITH THE VARYING LOAD
CONDITIONS AND KEEPS THE MEAN SPEED WITHIN CERTAIN LIMITS.
THE GOVERNORS MAY, BROADLY,
BE CLASSIFIED AS
1.
CENTRIFUGAL GOVERNOR
2.
INERTIA GOVERNOR
THE CENTRIFUGAL GOVERNORS
MAY FURTHER BE CLASSIFIED AS FOLLOWS:
I.
PENDULUM TYPE (WATT
GOVERNOR)
II.
LOADED TYPE
III.
DEAD WEIGHT GOVERNOR
(PORTER GOVERNOR AND PROELL GOVERNOR)
IV.
SPRING CONTROLLED GOVERNORS
(HARTNELL GOVERNOR, HARTUNG GOVERNOR, WILSON-HARTNELL GOVERNOR AND PICKERING
GOVERNOR).
WATT GOVERNOR: - THE SIMPLEST FORM OF A CENTRIFUGAL GOVERNOR IS A WATT GOVERNOR. IT
IS BASICALLY A CONICAL PENDULUM WITH LINKS ATTACHED TO A SLEEVE OF NEGLIGIBLE
MASS. THE ARMS OF THE GOVERNOR MAY BE CONNECTED TO THE SPINDLE IN THE FOLLOWING
THREE WAYS:
- THE PIVOT P MAY BE ON THE SPINDLE
AXIS.
- THE PIVOT P MAY BE OFFSET FROM THE
SPINDLE AXIS AND THE ARMS WHEN PRODUCED INTERSECT AT O.
- THE PIVOT P MAY BE OFFSET, BUT THE
ARMS CROSSES THE AXIS AT O.
PORTER GOVERNOR: - THE PORTER GOVERNOR IS A MODIFICATION OF A WATT’S GOVERNOR, WITH
CENTRAL LOAD ATTACHED TO THE SLEEVE. THE LOAD MOVES UP DOWN THE CENTRAL
SPINDLE. THIS ADDITIONAL DOWNWARD FORCE INCREASES THE SPEED OF REVOLUTION
REQUIRED TO ENABLE THE BALLS TO RISE TO ANY TO ANY PRE-DETERMINED LEVEL.
OBSERVATION:-
·
MASS OF THE BALL (M) =
————-KG.
·
WEIGHT OF THE BALL
(W)=————NEWTONS
·
HEIGHT OF THE GOVERNOR (H)
= ——- METRES
·
MINIMUM EQUILIBRIUM SPEED
(N1) = —— R.P.M.
·
MINIMUM EQUILIBRIUM SPEED
(N2) = —— R.P.M.
·
FRICTIONAL FORCE (F) =
————- NEWTONS
·
MEAN EQUILIBRIUM SPEED (N)
= (N1 + N2)/2 IN R.P.M
·
MASS OF THE CENTRAL LOAD =
———KG.
·
WEIGHT OF THE CENTRAL LOAD
(W) = ——–N
·
ANGLE OF INCLINATION OF THE
ARM TO THE VERTICAL (Α ) = ——
·
ANGLE OF INCLINATION OF THE
LINK TO THE VERTICAL (Β ) = ——
CALCULATION:-
·
N2 = 895/H
(FOR WATT GOVERNOR)
·
N2 = ((M
+ M (1+Q)/2)/M) X (895/H) (FOR PORTER GOVERNOR ), WHERE, Q
= TAN Β/ TAN Α
·
SENSITIVENESS OF THE
GOVERNOR = 2(N1 – N2)/ N1 + N2 =
2 (Ω2 – Ω1)/ Ω2 + Ω1
·
A GOVERNOR IS SAID TO BE
STABLE WHEN FOR EVERY SPEED WITHIN THE WORKING RANGE THERE IS A DEFINITE
CONFIGURATION I.E; THERE IS ONLY ONE RADIUS OF ROTATION OF THE GOVERNOR BALLS
AT WHICH THE GOVERNOR IS IN EQUILIBRIUM. FOR A STABLE GOVERNOR, IF THE
EQUILIBRIUM SPEED INCREASES, THE RADIUS OF GOVERNOR BALLS MUST ALSO
INCREASE.
OBSERVATION TABLE
WATT GOVERNOR (WITHOUT WEIGHT)
·
LENGTH OF EACH
LINK L=120MM
·
INITIAL HEIGHT OF
GOVERNOR H0=110MM
·
INITIAL RADIUS OF
ROTATION RO=135MM
·
WEIGHT OF SLEEVE W=1.8
KG
S.
NO.
|
SPEED‘N’
|
SLEEVE DISP.‘X’
|
HEIGHT H =H0-(X/2)
|
FIND Α
COS Α
=H/L
|
RADIUS OF ROTATION R = R0=L
SINΑ
|
W=(2ΠN/T)
|
FORCE (F) =(W(W2XR))/G
|
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1
|
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2
|
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3
|
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UNIVERSAL GOVERNOR APPARATUS
PORTER GOVERNOR (WITH WEIGHT):
·
LENGTH OF EACH LINK L
= 120MM
·
INITIAL HEIGHT OF
GOVERNOR H0=110MM
·
INITIAL RADIUS OF
ROTATION RO=135MM
·
WEIGHT OF BALLS+
SLEEVE W=1+1.8 KG=2.8KG
S.
NO.
|
SPEED
‘N’
|
SLEEVE DISP.
‘X’
|
HEIGHT H =H0-(X/2)
|
FIND Α COS Α = H/L
|
RADIUS OF ROTATION R=R0=L
SINΑ
|
W=(2ΠN/T)
|
FORCE F =(W(W2XR))/G
|
1
|
|||||||
2
|
|||||||
3
|
UNIVERSAL GOVERNOR
APPARATUS
HARTNELL GOVERNOR:
·
LENGTH OF EACH LINK A
= 75MM
·
LENGTH OF EACH LINK B
= 155MM
·
INITIAL RADIUS OF
ROTATION RO=160MM
·
WEIGHT OF SLEEVE W
=1.8 KG
·
T = 60SEC
S.NO.
|
SPEED ‘N’
|
SLEEVE DISP. ‘X’
|
HEIGHT R = (RO+(A/B).X)/10
|
W=(2ΠN/T)
|
FORCE F = W.W2.R
|
1
|
|||||
2
|
|||||
3
|
UNIVERSAL GOVERNOR APPARATUS
PROELL GOVERNOR:
·
LENGTH OF EACH
LINK L=125MM
·
INITIAL HEIGHT OF
GOVERNOR H0=100MM
·
INITIAL RADIUS OF
ROTATION RO=135MM
·
WEIGHT OF BALLS W=0.5
KG
·
EXTENSION OF
LENGTH BG= 75MM
S.NO.
|
SPEED
‘N’
|
SLEEVE DISP.
‘X’
|
HEIGHT
H
=
H0-(X/2)
|
FINDΑ COSΑ
=
H/L
|
RADIUS OF ROTATION R=R0=L
SINΑ
|
W=(2ΠN/T)
|
FORCE F =(W(W2XR))/G
|
1
|
|||||||
2
|
|||||||
3
|
PRECAUTIONS:-
- TAKE READING CAREFULLY.
- MEASURE THE ANGLE VERY CAREFULLY.
- MEASURE THE HEIGHT OF GOVERNOR
CAREFULLY.
- SPEED OF GOVERNOR MEASURE ACCURATE.
EXPERIMENT - 6
OBJECTIVE: TO FIND CORIOLLIS COMPONENT OF ACCELERATION AND VERIFY
THE RESULT.
THEORY: IF A POINT IS MOVING ALONG A LINE, WITH THE LINE HAVING ROTATIONAL
MOTION THE ABSOLUTE ACCELERATION OF THE POINT IS VECTOR SUM OF –Ω. ABSOLUTE
ACCELERATION OF COINCIDENT POINT OVER THE LINK RELATIVE TO FIXED CENTRE.
ACCELERATION OF POINT UNDER
CONSIDERATION RELATIVE TOP COINCIDENT POINT AND THE THIRD COMPONENT CALLED
CORIOLLIS COMPONENT OF ACCELERATION.
CONSIDER THE MOTION OF
SLIDER ‘B’ ON THE CRANK OA.LET OA ROTATE WITH CONSTANT ANGULAR VELOCITY OF Ω
RAD/SEC AND SLIDER B HAVE A RADIAL OUTWARD VELOCITY V M/SEC RELATIVE TO CRANK
CENTRE ‘O’.
IN THE VELOCITY DIAGRAM OA
REPRESENT TANGENTIAL VELOCITY SLIDER AT CRANK POSITION OA, AND AB REPRESENT
RADIAL VELOCITY OF SLIDER AT SAME CRANK POSITION. OA IS THE TANGENTIAL VELOCITY
OF SLIDER AT CRANK POSITION OA AND AB REPRESENT RADIAL VELOCITY OF SLIDER AT
SAME POSITION.
HENCE BB’ REPRESENT THE
RESULTANT CHANGE OF VELOCITY OF SLIDER.THIS VELOCITY HAS TWO COMPONENT B’T AND
BT IN TANGENTIAL AND RADIAL DIRECTIONS RESPECTIVELY.
NOW, THE TANGENTIAL
COMPONENT, B’T
= B’S+ST
= VSINDѲ + (Ω(R+DR)-ΩR)
= VDѲ+ΩDR
THERE FORE RATE OF CHANGE
OF TANGENTIAL VELOCITY
= VDѲ/DT + ΩDR/DT
= VΩ+ΩV
= 2VΩ
EQUATION REPRESENT
CORIOLLIS COMPONENT OF ACCELERATION .THIS ACCELERATION IS MADE UP OF TWO
COMPONENTS, ONE DUE TO INCREASE IN RADIUS AND OTHER FROM CHANGE IN DIRECTION OF
CRANK.
HYDRAULIC ANALOGY:
CONSIDER A SHORT COLUMN OF
FLUID OF LENGTH DR AT RADIUS R FROM AXIS OF ROTATION OF THE TUBE.THEN IF
VELOCITY OF FLUID RELATIVE TO TUBE IS V AND ANGULAR VELOCITY OF TUBE ISΩ THEN
CORIOLLIS COMPONENT OF ACCELERATION IS 2V Ω IN A DIRECTION PERPENDICULAR TO
ROTATION OF TUBE.THE TORQUE DT APPLIED BY THE TUBE TO PRODUCE THIS ACCELERATION
IS THEN
DT=DW.2VΩR/G
WHERE DW IS WEIGHT OF SHORT
COLUMN OF FLUID.
IF W BE THE SPECIFIC WEIGHT
OF FLUID AND A IS CROSSECTIONAL AREA OF TUBE, THEN
DW=WADR
DT=WADR/G=2VRΩ
AND TOTAL TORQUE APPLIED TO
COLUMN OF LENGTH L.
T=2WL\G.VΩ.A.R.DR
T=W\G.2ΩV.A.L
THEREFORE, CORIOLLI’S
COMPONENT OF ACCELERATION.
CA= 2GT\2WAL
THE APPARATUS:
T HE APPARATUS USES
HYDRAULIC ANALOGY TO DETERMINE CORIOLLI’S COMPONENT OF ACCELERATION.
THE APPARATUS CONSIST OF
TWO BRASS TUBES CONNECTED TO A CENTRAL ROTOR DISTRIBUTOR. THE
DISTRIBUTOR IS ROTATED BY A
VARIABLE SPEED D.C MOTOR. WATER IS SUPPLIED TO A DISTRIBUTOR BY A PUMP THROUGH.
WHEN TUBES ARE ROTATING WITH FLOWING THROUGH TUBES WITH VARIOUS EASUREMENTS
PROVIDED, CORIOLLI’S COMPONENT CAN BE DETERMINED EXPERIMENTELY AND
THEORETICALY.
PROCEDURE:
FILL- UP SUFFICIENT WATER
IN TANK. ROTATE THE COUPLING TO ENSURE FREE ROTATION. CHECK NUT BOLTS FOR
TIGHTENING. START THE MOTOR AND SET THE SPEED AS REQUIRED, E.G SAY 150 RPM.
MEASURE THE TORQUE REQUIRED FOR FREE ROTATION OF TUBES AT THAT SPEED.
NOW START THE PUMP AND
ADJUST THE FLOW RATE WITH HELP OF BY- PASS VALVE, SO THAT WATER DOES NOT
OVERFLOW THROUGH CENTRAL GLASS TUBE AND ALSO PIPES RUN FULL OF WATER. NOW
ADJUST THE SPEED TO PREVIOUS
VALUE AND MEASURE THE
TORQUE. NOTE DOWN WATER FLOW RATE. REPEAT THE PROCEDURE AT DIFFERENT SPEEDS.
OBSERVATION TABLE:
DIAMETER OF FLOW TUBE=6MM
=0.006M
ARM LENGTH =200MM=0.2M
G=9.81KG/M2
W=DENSITY OF WATER
=1000KG/M2
EXPERIMENT - 7
AIM: TO STUDY THE AUTOMATIC TRANSMISSION UNIT
GEAR BOX OR TRANSMISSION
‘TRANSMISSION’ WORD IS
GENERALLY USED FOR GEAR BOX. TRANSMISSION IS A MECHANISM WHICH PROVIDES US
VARIATION IN SPEED AND TORQUE AS REQUIRED. THE TRANSMISSION MAY BE MANUAL OR
AUTOMATIC.
FUNCTIONS OF GEAR BOX OR TRANSMISSION
·
A LOT OF VARIATION IN
TORQUE IS REQUIRED AT ROAD WHEEL OF A VEHICLE. A GEAR BOX SERVES THIS PURPOSE.
IT PROVIDES HIGH TORQUE AT STARTING AND HIGH SPEED WHILE RUNNING.
·
GEAR BOX ALSO PROVIDES
MEANS TO REVERSE THE DIRECTION OF THE VEHICLE.
·
IT PROVIDES A NEUTRAL
POSITION, THE POSITION AT WHICH THE POWER FLOW TO ROAD WHEELS IS DISCONNECTED.
NECESSITY OF TRANSMISSION
THERE ARE MANY RESISTANCES
FACED BY VEHICLE WHILE RUNNING. ALSO WHEN VEHICLE IS ON THE VERGE TO MOVE,
THERE ARE ALSO RESISTANCES WHICH OPPOSE ITS MOVEMENT. TO OVERCOME THESE
RESISTANCES, TRANSMISSION IS A MECHANISM WHICH IS NECESSARY TO BE USED.
THE FOLLOWING RESISTANCE
ARE FACED BY THE VEHICLE:
- ROLLING
RESISTANCE
IT IS OBSERVED THAT MORE
FORCE IS REQUIRED TO MOVE A STATIONARY VEHICLE AND ONCE IT STARTS MOVING OR
ROLLING, THE FORCE REQUIRED TO KEEP IT MOVING IS LESSER. THE RESISTANCE, WHICH
COMES INTO PLAY HERE, IS CALLED ROLLING RESISTANCE. IT DEPENDS UPON THE
FOLLOWING FACTORS:
·
CONDITION OF ROAD
·
CONDITION OF TYRES
·
TYRE INFLATION
·
VEHICLE LOAD INCLUDING
CARRIAGE
·
TYPE OF TYRES
- AIR
RESISTANCE
WHEN THE VEHICLE IS
STATIONARY, IT FACES THE RESISTANCE OF BLOWING AIR ONLY. TO START MOVING, IT
HAS TO OVERCOME THIS RESISTANCE. BUT WHEN THE VEHICLE IS MOVING, THE AIR
RESISTANCE INCREASES, BECAUSE VELOCITY OF AIR STRIKING THE VEHICLE IS
INCREASED. THIS RESISTANCE IS PROPORTIONAL TO THE SQUARE OF THE VELOCITY OF THE
AIR. SO, IF THE AIR VELOCITY IS DOUBLED, THE AIR RESISTANCE INCREASES FOUR
TIMES. TO LESSEN THIS RESISTANCE, THE VEHICLE’S FRONT BODY SHAPE IS MADE
STREAMLINED.
- GRADIENT
RESISTANCE
THIS RESISTANCE IS DUE TO
THE INCLINATION OF THE ROAD TO HORIZON. WHEN CLIMBING UP, THE VEHICLE FACES MORE
RESISTANCES THAN DOWN-HILL MOVEMENT.
- TRACTIVE
EFFORT
THE SUM OF ALL THE ABOVE
THREE RESISTANCES IS CALLED TOTAL RESISTANCE OR TRACTIVE RESISTANCE.
TRACTIVE RESISTANCE =
ROLLING RESISTANCE + AIR RESISTANCE + GRADIENT RESISTANCE.
TRACTIVE EFFORT IS THE DRIVING
FORCE REQUIRED TO PROPEL THE VEHICLE I.E. TO OVERCOME THE TRACTIVE RESISTANCE.
THIS EFFORT VARIES ACCORDING TO THE DRIVING CONDITIONS. TO MOVE A VEHICLE FROM
STATIONARY OR CLIMBING A HILL, HIGH ENGINE SPEED IS REQUIRED. BUT THE ENGINE
SPEED HAS ITS LIMITATIONS. SO A LOW GEAR HELPS TO MOVE A VEHICLE. THUS A GEAR
BOX IS NECESSARY FOR A VEHICLE.
SELECTIVE TYPE GEAR BOX
IN THIS TYPE, ANY GEAR MAY
SHIFTED FROM NEUTRAL POSITION AND EVERYTIME WHILE SHIFTING THE GEAR, WE HAVE TO
GO TO NEUTRAL POSITION FIRST AND THEN TO THE OTHER GEAR POSITION.
SLIDING MESH GEAR BOX
CONSTRUCTION
THIS TYPE OF GEAR BOX IS
SHOWN IN FIG.1. BY A SIMPLE DIAGRAM IN NEUTRAL POSITION. THERE IS A GEAR CALLED
CLUTCH GEAR WHICH IS MOUNTED ON THE CLUTCH SHAFT. THIS GEAR BOX SHAFT IS ATTACHED
TO THE CLUTCH. THE CLUTCH GEAR A IS ALWAYS MESHED WITH LAY SHAFT GEAR D. THE
LAY SHAFT GEAR IS MOUNTED ON A SHAFT WHICH IS CALLED LAY SHAFT.
THERE ARE THREE OTHER GEARS
E, F AND G, FIXED ON THE LAY SHAFT. THERE IS ALSO AN IDLE SHAFT ON WHICH A
SMALL IDLE GEAR ‘H’ IS MOUNTED. THIS IDLE GEAR IS USED FOR REVERSING THE
DIRECTION. THERE IS A MAIN SHAFTB WHICH IS ALIGNED TO THE CLUTCH SHAFT. TWO
GEARS ‘B’ AND ‘C’ ARE MOUNTED ON THE MAIN SHAFT SUCH THAT THEY CAN SLIDE ON THE
SHAFT.
WORKING
FIG. 1 SHOWS A SLIDING MESH
GEAR BOX IS NEUTRAL POSITION. THE GEAR ‘A’ IS ALWAYS ROTATING WHEN THE CLUTCH
IS ENGAGED. THE GEARS ‘D’ ‘E’ ‘F’ ‘G’ AND ‘H’ ALSO ROTATE WITH GEAR ‘A’.
NEITHER GEAR ‘B’, NOR GEAR ‘C’ IS MESHED WITH ANY OF THE GEAR OF THE SHAFT.
SO NO POWER IS TRANSMITTED
TO MAIN SHAFT. IN THIS POSITION THE GEAR BOX IS IN NEUTRAL POSITION.
FIRST GEAR: TO POSITION THE GEAR BOX IN FIRST GEAR (FIG.2.) THE GEAR C IS
SLIDED ON THE MAIN SHAFT SUCH THAT IT IS MESHED WITH GEAR F. NOW THE MAIN SHAFT
STARTS ROTATING. THE POWER IS TRANSMITTED FROM CLUTCH SHAFT THROUGH GEARS A, D,
F AND C TO THE MAIN SHAFT.
SECOND GEAR: TO POSITION THE GEAR BOX
IN SECOND GEAR. (FIG.3), THE GEAR B IS SLIDED ON THE MAIN SHAFT SUCH THAT IT IS
MESHED WITH GEAR E. NOW THE POWER IS TRANSMITTED FROM CLUTCH SHAFT THROUGH
GEARS A,D,E AND B TO THE MAIN SHAFT.
HIGH GEAR OR TOP GEAR: TO POSITION THE GEAR BOX IN HIGH GEAR (FIG.4), THE GEAR B IS
SLIDED ON THE MAIN SHAFT SUCH THAT IT IS DIRECTLY ENGAGED TO GEAR THROUGH
SPLINES. SO THE POWER IS TRANSMITTED TO MAIN SHAFT WITHOUT ANY REDUCTION.
REVERSE GEAR: TO POSITION THE GEAR BOX IN REVERSE GEAR (FIG.5), THE GEAR C
IS SLIDED ON THE MAIN SHAFT SUCH THAT IT IS MESHED WITH THE IDLE GEAR H. BY
DOING THIS THE GEAR H REVERSE THE DIRECTION OF ROTATION OF MAIN SHAFT. IN THIS
POSITION POWER IS TRANSMITTED FROM CLUTCH SHAFT THROUGH GEARS A, D, G, H AND C
TO THE MAIN SHAFT.
EXPERIMENT - 8
AIM: TO STUDY AND PREPARE REPOT ON THE CONSTRUCTIONAL DETAILS,
WORKING PRINCIPLES AND OPERATION OF AUTOMOTIVE BRAKE SYSTEMS.
A.
HYDRAULIC AND PNEUMATIC
BRAKE SYSTEMS
B.
DRUM BRAKE SYSTEM
C.
DISC BRAKE SYSTEM
THEORY:
LABELLED DIAGRAM,
CONSTRUCTIONAL DETAILS, WORKING PRINCIPLE AND OPERATION OF THE ABOVE STEERING
SYSTEMS.
PRINCIPLE:
IT GOES WITHOUT SAYING THAT
BRAKES ARE ONE OF THE MOST IMPORTANT CONTROL COMPONENTS OF VEHICLE. THEY ARE
REQUIRED TO STOP THE VEHICLE WITHIN THE SMALLEST POSSIBLE DISTANCE AND THIS IS
DONE BY CONVERTING THE KINETIC ENERGY OF THE VEHICLE INTO THE HEAT ENERGY WHICH
IS DISSIPATED INTO THE ATMOSPHERE.
BRAKING REQUIREMENTS
·
THE BRAKES MUST BE STRONG
ENOUGH TO STOP THE VEHICLE WITHIN A MINIMUM DISTANCE IN AN EMERGENCY. BUT THIS
SHOULD ALSO BE CONSISTENT WITH SAFETY. THE DRIVER MUST HAVE PROPER CONTROL OVER
THE VEHICLE DURING EMERGENCY BRAKING AND THE VEHICLE MUST NOT SKID.
·
THE BRAKES MUST HAVE GOOD
ANTIFADE CHARACTERISTICS I.E. THEIR EFFECTIVENESS SHOULD NOT DECREASE WITH
CONSTANT PROLONGED APPLICATION E.G. WHILE DESCENDING HILLS. THIS REQUIREMENT
DEMANDS THAT THE COOLING OF THE BRAKES SHOULD BE VERY EFFICIENT.
HYDRAULIC BRAKES
MOST OF THE CARS TODAY USE
HYDRAULICALLY OPERATED FOOT BRAKES ON ALL THE FOUR WHEELS WITH AN ADDITIONAL
HAND BRAKE MECHANICALLY OPERATED ON THE REAR WHEELS. AN OUTLINE OF THE
HYDRAULIC BRAKING SYSTEM IS SHOWN IN FIG. THE MAIN COMPONENT IN THIS IS THE
MASTER CYLINDER WHICH CONTAINS RESERVOIR FOR THE BRAKE FLUID. MASTER CYLINDER
IS OPERATED BY THE BRAKE PEDAL AND IS FURTHER CONNECTED TO THE WHEEL CYLINDERS
IN EACH WHEEL THROUGH STEEL PIPE LINES, UNIONS AND FLEXIBLE HOSES. IN CASE OF
HINDUSTAN AMBASSADOR CAR, ON FRONT WHEELS EACH BRAKE SHOE IS OPERATED BY
SEPARATE WHEEL CYLINDER (THUS MAKING THE BRAKE TWO SHOE LEADING) WHEREAS IN
CASE OF REAR WHEELS THERE IS ONLY ONE CYLINDER ON EACH WHEEL WHICH OPERATES
BOTH THE SHOES (THUS GIVING ONE LEADING AND ONE TRAINING SHOE BRAKES.) AS THE
REAR WHEEL CYLINDERS ARE ALSO OPERATED MECHANICALLY WITH THE HAND BRAKE,
THEY ARE MADE FLOATING. FURTHER, ALL THE SHOES IN THE AMBASSADOR CAR ARE OF THE
FLOATING ANCHOR TYPE.
THE SYSTEM IS SO DESIGNED
THAT EVEN WHEN THE BRAKES ARE IN THE RELEASED POSITION, A SMALL PRESSURE OF
ABOUT 50 KPA IS MAINTAINED IN THE PIPE LINES TO ENSURE THAT THE CUPS OF THE
WHEEL CYLINDER ARE KEPT EXPANDED. THIS PREVENTS THE AIR FROM ENTERING THE WHEEL
CYLINDERS WHEN THE BRAKES ARE RELEASED. BESIDES, THIS PRESSURE ALSO SERVES THE
FOLLOWING PURPOSES.
·
IT KEEPS THE FREE TRAVEL OF
THE PEDAL MINIMUM BY OPPOSING THE BRAKE SHOE RETRACTION SPRINGS.
·
DURING BLEEDING, IT DOES
NOT ALLOW THE FLUID PUMPED INTO THE LINE TO RETURN, THUS QUICKLY PURGING AIR
FROM THE SYSTEM.
DRUM BRAKES
IN THIS TYPE OF BRAKES, A
BRAKE DRUM IS ATTACHED CONCENTRIC TO THE AXLE HUB WHEREAS ON THE AXLE CASING IS
MOUNTED A BACK PLATE. IN CASE OF FRONT AXLE, THE BACK PLATE IS BOLTED TO THE
STEERING KNUCKLE. THE BACK PLATE IS MADE OF PRESSED STEEL SHEET AND IS RIBED TO
INCREASE RIGIDITY AND TO PROVIDE SUPPORT FOR THE EXPANDER, ANCHOR AND BRAKE
SHOES. IT ALSO PROTECTS THE DRUM AND SHOE ASSEMBLY FROM MUD AND DUST. MOREOVER,
IT ABSORBS THE COMPLETE TORQUE REACTION OF THE SHOES DUE TO WHICH REASON IT IS
SOMETIMES ALSO CALLED TORQUE PLATE. TWO BRAKE SHOES ARE ANCHORED ON THE BACK
PLATE AS SHOWN IN FIG. FRICTION LININGS ARE MOUNTED ON THE BRAKE SHOES. ONE OR
TWO RETRACTOR SPRINGS ARE USED WHICH SERVE TO KEEP THE BRAKE SHOES AWAY FROM
THE DRUM WHEN THE BRAKES ARE
NOT APPLIED. THE BRAKE
SHOES ARE ANCHORED AT ONE END, WHEREAS ON THE OTHER ENDS FORCE F IS APPLIED BY
MEANS OF SOME BRAKE ACTUATING MECHANISM WHICH FORCES THE BRAKE SHOE AGAINST THE
REVOLVING DRUM, THEREBY APPLYING THE BRAKES. AN ADJUSTER IS ALSO PROVIDED TO
COMPENSATE FOR WEAR OF FRICTION LINING WITH USE. THE RELATIVE BRAKING TORQUE
OBTAINED AT THE SHOES FOR THE SAME FORCE APPLIED AT THE PEDAL VARIES DEPENDING
UPON WHETHER THE EXPANDER (CAM OR TOGGLE LEVER) IS FIXED TO THE BACK PLATE OR
IT IS FLOATING, WHETHER THE ANCHOR IS FIXED OR FLOATING AND WHETHER THE SHOES
ARE LEADING OR TRAILING.
DISC BRAKES
AS SHOWN IN FIG. A DISC
BRAKE CONSISTS OF A CAST IRON DISC BOLTED TO THE WHEEL HUB AND A STATIONARY
HOUSING CALLED CALIPER. THE CALIPER IS CONNECTED TO SOME STATIONARY PART OF THE
VEHICLE, LIKE THE AXLE CASING OR THE SUB AXLE AND IS CAST IN TWO PARTS, EACH
PART CONTAINING A PISTON. IN BETWEEN EACH PISTON AND DISC, THERE
IS FRICTION PAD HELD IN POSITION BY RETAINING PINS, SPRING PLATES ETC.
PASSAGES ARE DRILLED IN THE CALIPER FOR THE FLUID TO ENTER OR LEAVE EACH
HOUSING. THESE PASSAGES ARE ALSO CONNECTED TO ANOTHER ONE FOR BLEEDING. EACH
CYLINDER AND CONTAINS A RUBBER SEALING RING BETWEEN THE CYLINDER AND THE PISTON.
WHEN THE BRAKES ARE
APPLIED, HYDRAULICALLY ACTUATED PISTONS MOVE THE FRICTION PADS INTO CONTACT
WITH THE DISC, APPLYING EQUAL AND OPPOSITE FORCES ON THE LATER. ON RELEASING
THE BRAKES, THE RUBBER SEALING RINGS ACT AS RETURN SPRINGS AND RETRACT THE PISTONS
AND THE FRICTION PADS AWAY FROM THE DISC.
FOR A BRAKE OF THIS TYPE
T = 2µPAR
WHERE
µ = COEFFICIENT OF FRICTION
P = FLUID PRESSURE
A = CROSS SECTIONAL AREA OF
ONE PISTON
R = DISTANCE OF THE
LONGITUDINAL AXIS OF THE PISTON FROM THE WHEEL AXIS
BRAKE SYSTEM FOR MARUTI (SUZUKI) 800 CAR
THE FRONT WHEEL BRAKES ARE
OF THE DISC TYPE, WHEREAS FOR REAR WHEELS DRUM TYPE BRAKES (LEADING TRAILING
SHOES) ARE EMPLOYED. PARKING BRAKE IS MECHANICALLY OPERATED BY A WIRE AND LINK
SYSTEM AND WORKS ON THE REAR WHEELS ONLY. SAME BRAKE SHOES ARE USED FOR SERVICE
AND PARKING BRAKES. THE LAYOUT OF THE SYSTEM IS SHOWN IN FIG.
A TANDEM MASTER CYLINDER IS
EMPLOYED. THE HYDRAULIC PRESSURE PRODUCED THERE IS APPLIED TO TWO INDEPENDENT
CIRCUITS. ONE CIRCUIT IS FOR FRONT LEFT AND REAR RIGHT BRAKES, WHEREAS THE
OTHER IS FOR FRONT RIGHT AND REAR LEFT BRAKES. DUE TO THIS REASON, THE BRAKING
SYSTEM IN THE MARUTI HAS GREATER SAFETY BECAUSE EVEN IF A PRESSURE LEAK OCCURS
IN THE BRAKE LINE OF ONE CIRCUIT, THE OTHER BRAKING CIRCUIT WORKS, DUE TO WHICH
A CERTAIN DEGREE OF BRAKING IS STILL AVAILABLE TO THE VEHICLE.
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